Hi. I can't honestly claim to recommend these rectifiers:-
eBay item number:184534154463
from first hand experience because I haven't made use of one in a welder for any length of time yet. I have tried two in two seperate machines and they have worked fine and showed no signs of being stressed or overheating. Both machines were just experiments so far and have not had a lot of time in use so no long term reliability experience. If you were to buy a unit rated well over the current of the machine- say 300amps for your welder- and mount it on a good sized piece of aluminium it could be a cheap replacement at around £30. Just an idea.
the really strage thing is the machine has done nothing when i got it secodhand its was unmarked as near to showroom as you can get so may be just one of them thingswith regards the bridge going like thative had it 2 years about time i fixed it