Wilkinson's sells a small (but plentiful) pot of dried meal worms for a good price, I think it's about 100g for £2 (Not on the website, but a 3L version is if you have PLENTY of meal worm hungry hams). Be careful to crush the heads of live meal worms so they don't bite the ham's pouches. All of my hamsters, a syrian, 2 russians, 2 robos and a hybrid love the dried variety - they literally snatch them out of my fingers. You kind of get used to them - I didn't like touching them at first. I'm still not brave enough to try the live variety!
I have seen 'flavored' meal worms aimed at birds, but they seem to be pretty rare. I wouldn't risk anything like that. Hams like them plenty enough flavoured naturally! In fact, I don't even know why birds would want them berry flavoured.