There are a whole host of creative people out there catering to the wedding stationery market. Folksy boasts a 'Wedding' section and amongst all the handmade jewellery, there are several crafty bods selling handmade wedding stationery.
Here are two sellers I've found on Folksy:
Alternatively, to give you some creative control and perhaps save some money, you could purchase handmade cards that are blank inside and create your own insert with the invitation details. I sell handmade cards in my Foksy shop that are without inserts, giving people the opportunity to create their own invitations for special occassions.
Before you invest your money in the whole stationery range, it is worth seeing some samples to check the quality and design. As handmade items are generally made to order, if you want a design changing in some way, ask. The beauty of handmade is that it can be change and made to be even more unique.