The best metal and materials supplier you can find is your own mouth.
Tell everyone you know that you can use any sorts of offcuts, and you will soon find that over time, when people are having a clearout of garages and sheds they will think of you. Friends, neighbours, workmates, even people down the pub. Even an old computer printer will have loads of useful bits inside, it just takes a little time to get to them.
It doesn't get the right material at the right time, but you soon build up a stock of allsorts.
I keep most of mine in a large plastic storage box outside in the garden, and a quick rummage thru will soon turn up something that is ideal for the job.
Maybe a little on the large side for making model boats, but this is how most of my material gets to me. Throwaway bits of no further use to anyone. BTW, they are sitting on top of my outside storage box. Even the 4ft x 4ft sheets of 10mm thick perspex were discards, and even though not for use yet, they are earmarked for a major job in the near future.
A little bit of work.
And it becomes very useable material, the big blue discs are 3.5" diameter cast iron.
And these are donation boxes of bits and pieces, sorted into usefull bits. This is only part of it, wire and rod is stored in another area, and most of it was free.
Basically, nothing is thrown away until it truly has no further use.
All you need to do is open your mouth, and have a little bit of insight into how to get the best out of what you have been given. It most probably won't be spot on for the job, but with a little work, it can be made to be.
Bogs