I have a Lyman GPR and a GPH. Both are a bit heavy and long to carry afield. A Mountain Rifle would be similar. TC Renegades and Hawkins are lighter, but are no longer made. I started out with a Hawken, but TC was still making them then. But, as others have said, there's a lot of them around. If you have problems, you could always pick up another as a 'parts daisy'.
However, starting out now, I'd take a long look at the Lyman Deer Stalker. It's light, handy, accurate and made to be carried afield. It's not as traditional as a GPR or a Mountain Rifle, but it'll be easier to live with. Plus, it's still being made (or will be once the Italians recover from Covid). If you like the idea of Patched Roundball, look at the .54.