Should be the same inlet as any Ruger M77 MkII Short Action. Since it's the Frontier, it's in a compact stock. Richard's Micro fit, Stocky's Stocks, Boyd's, Midway, Brownell, etc etc all offer these stocks.
Here's a link to one at Midway, showing in stock right now for $165, should fairly closely replicate the factory stock.
When you said "Composite" my mind goes to "composite materials" i.e. plywood, aka "laminate."
Are you looking for a synthetic stock?
Not sure anyone sells a compact synthetic stock, but the standard stock will fit just fine. I'd expect there would be someone out there that makes a compact synthetic, but I don't see one at Midway or Brownells right now.
Although, to be honest, I'm not 100% sure I don't believe I couldn't lighten a laminate compact stock to less than a synthetic stock that was properly bedded and stiffened.