THose balloon clips are useless, they let too much air leak out. UNless you have more than a few hundred balloons, tying them is still best. If you practice, you can get really quick at tying balloons. Aim to do a single overhand knot by pulling the end of the balloon around so it falls through the knot easily, and you're not trying to tithe knot back to front, if you get my meaning.
The gas tanks are likely to label the gas "balloon gas" which is a fraction of the price of pure helium. If you use pure helium, the gas will still leak out but the balloon will be empty. With balloon gas (mostly air but enough helium to lift the balloon) then when the helium component has leaked out, the balloon still looks mostly inflated.
Printing signs - ring a local printer and ask them what they can do for you. If you have the capability with the graphics, work on the poster design yourself and save it as a PDF. Then email it to the printer and ask them for quotes. If you don't know their work, ask to see samples. Drop in for a visit if you can.
One cheap option would be to laminate your own posters. Or slip them into plastic sleeves and staple those to a telegraph pole. How many? Sourcing online - I wouldn't, I would check for local print houses in your area. Get to know them, use them for other services. I've now got my favourite printer that I use for all sorts of jobs now, as well as recommend them to others. They did the wedding invitations for difficult child 1, which were printed onto photos.
If your board member were in Australia and trying to use his position on the board to get business his way, that would be illegal. Our laws of incorporation mean that a board member may not influence decisions that could lead to personal profit. I had a similar situation happen some years ago - a writing group I belonged to was chaired by a woman with her own printing business. When our group was publishing an anthology, this woman made sure her company won the printing job, because she controlled all the quotes, all the information etc. It was very naughty and frankly, it cost us more than I think it should have. I actually decided, at the launch of that anthology, to produce my own book, all by myself, even though I did not have my own publishing company. Ten weeks later, my book was released. Per item it cost a fraction of the one the group had brought out, and I have sold more copies. I learned a great deal in the process and managed to do a few unique things with it, that my publisher 'friend' still hasn't been able to work out.
So have faith in yourself. But the way to do it with the board, is to make up the poster, get some quotes and present the quotes to the board. To make sure your quotes are all comparing apples with apples, make sure you ask for exactly the same thing in your quotes (ie 150 posters, full colour, laminated, X size on Y grade of card). If you can, have samples from each printer, put it all in a written summary with your recommendation.
A board I was on some years ago, had a woman on it who resented my involvement with the journal we published. We had a system in place, all the quote work etc had been done years earlier, but this woman felt she knew better (besides, I suspect a friend of hers was a printer and wanted the job). She organised quotes which did come in under the costs we were currently paying, but her quotes did not include the grade of paper. Or if they did, the grade of paper we found this printer was actually using, was far too thin and the print bled through. Looked awful. Also their quality control left a lot to be desired - the block of text on the page was rotated somewhat, the margins were uneven and the inner margin, which should always be wider than the outer margin, was thinner. It all looked awful. So make sure you have comparable quotes AND some samples of their work.
When you have a print job done, the printer should do a sample for you which you sign off on, before the full job is done. The sample gives you one last chance to change anything not quite right. But it should be very close by then, no major changes should be made at this last stage. I had one author who, at this last stage, decided to add a few more chapters. NOT acceptable!
So good luck with this one. You should be able to organise quotes with a day or two turnaround.
Marg