My local emporium cuts to size, and so do the first two internet suppliers I looked at after searching for 'buy metal cut to size'.
Unwillingness to cut may be a local thing – just after buying a mini-lathe, a place in Bristol refused to sell me anything in less than stock lengths, 10 or 12 feet.
I've noticed some trade-outlets are reluctant to sell bits and bobs to hobbyists, probably because of the admin overhead and fuss-factor. I find spending a hefty lump of money in one well organised go makes me a valued customer. The same dosh spread over several small purchases is less welcome, and they definitely don't like giving advice when they're busy!
Internet metal sellers seem more geared to retail customers, and I suppose smaller parcels of metal make delivery easy too.
Not necessarily cheap though!
Dave