There are many links to various laser parts dotted around my site, to make things easier I will bring these and more together here.
Before you buy online know who you are buying from, a lot of laser/parts sellers that you will come across are youngsters, still at school or college, they are not a shop/company/warehouse. This does not make them bad people, it does make it more likely that things could go wrong with your transaction. Having said that thousands of lasers and parts have been sold online, the vast majority of transactions go through with no problems, there will always be exceptions.
I suggest that before buying or selling online you read This thread
There are group buys and laser sales on this website all the time, the members there are friendly and helpful as long as you don't need to be spoon fed information. There is a very good search engine on the site, use it to help find what you want.
Always worth a look for low cost, good quality, green modules.