I have found VTI to be a very good source for parts and for prompt shipping.
I like them better than Taylor's for parts, and they are always courteous on the phone or email. The parts they have are not cheap, but they generally have what one needs.
I have like new Pietta 1851 Navy grip assembly for sale @$65 + ship and VTI has new like parts for $109 + ship.
From them I got a part round/part octagonal barrel and a smooth non-engraved cylinder for my Pietta L&R creation as Pietta does not market one, and a few years ago purchased a Pietta brass backstrap without the shoulder stock bottom divot to be historically correct. Those folks are very knowledgeable and I really appreciate that very much.
Regards,
Jim