There are some armour suppliers that provide building services at additional cost. AP, TM, CFO and RS most notably. AP is from Canada and have recently stopped taking new build orders to work on their backlog. TM, CFO and RS are both all the UK. CFO is best for a ROTJ style armour, and the others are best for ANH, although AP can also be used for some game related ANH/ROTJ hybrids.
When it comes to ANH, it's TM and RS that are without doubt the best you can find.
Although I think that you would find it fun to build yourself as well. It's not as hard as it looks, provides you with lots of skills and experience for doing more prop stuff further on, which I'm pretty sure you will. And you save a lot of money dong it yourself.