Just ideas, haven’t tried yet:
Take 20-inch pads, turn sideways, cut to desired width, use leftovers until you have as many 20-inch-long chunks as needed. Join together with tape, and roll or fold and tuck into backpack creatively.
Or cut those sideways trimmed-width pads into 5-inch-long chunks and zig-zag join with tape, roughly like a Z-Rest. Fold and strap onto backpack.
The Ridgerest Classic Large is 25 x 77 inches, but easily trimmed to desired length. Like your Z Lite Sol, the Ridgerest is R 2.0.
Check the R-values of other pads you consider. For example, the thickest MLD CCF pad is R 0.8, the Exped Flexmat LW is R 1.5, and the Exped Flexmat Plus LW is R 2.2. Good luck figuring out how much colder or warmer you might sleep at different R-values.
You could trim a wider CCF pad to 20 inches wide along your legs to save 1 or 2 ounces.
— Rex