1. Congratulations on buying the best BP revolver [for less than £900 or so] ever made.
2. Ruger stopped making them in April 2010 and a call to the factory last year for two action screws resulted in this conversation -
'tac, we originally hoped to have stocks of spares for the next ten years, but you know how it is....the screws you want, well, there are only four left on the planet, so I'll send them to the UK distributors - VIKING ARMS - so they can deal them out to you...' Nobody has Ruger spare parts to dish out except Viking Arms through your dealer.
3. That should have answered most of your questions.
BTW, for future reference and cocking a snoot at the UK 'authorities' - the Ruger Old Army was made and sold as a .44cal BP revolver, NOT a .45cal. The rather odd interpretation of the way that BP firearms shoot oversize bullets or balls is only to be found within the confines of the UK. Elsewhere, folks call them what the maker has called them since the day the very first one rolled off the line - a .44cal BP revolver.
The Ruger Old Army was designed to shoot a soft lead ball of .457" diameter - this assures anyone loading it that a goodly shaving is taken off and a good cylinder seal is thereby obtained. You can shoot whatever you like in it that you think is suitable - your choice - providing it doesn't actually either roll back out, or fly out on recoil. Me, I'll continue with the .457" Lee - 'Made for the Ruger Old Army' it says on the box - that I've been shooting since March 2nd, 1986.
Best
tac