First thing I do with a new rc is to replace all the screws. I use the black oxide, high strength alloy steel, grade 12.9 or 10.9 (smaller) hex screws and I use a set of Thorp drivers. Early on I found the SS ones are pretty, but strip when used more than several times and are not very strong.

I have bought screws from hexcrews, but just the kits for 18th scale and always black oxide. I've never had a problem with breakage or stripping heads on any of their screws.

All my bigger stuff comes from Tony's Screws - I haven't had any problems.