The original nipples should handle the #10 caps fine. That's what they are designed for.
Percussion caps are made by CCI, Remington, and RWS. All of whom manufacture ammunition and primers for reloading.
The muzzle loading market is overshadowed by the scarcity of ammunition and reloading primers. We in the black powder business probably represent only 10% to 15% of the sporting arms market.
If Hillary gets "The Ticket", ammunition and reloading components will be flying off the shelves, and percussion caps will have to "take a back seat".