Would like Underquilt that goes to about 20- 30 degrees

[LazyCamper]

What the title says. Maximum payment would be 80 dollars.

[HomeMadeHiker]

Repurposing a sleeping bag is a good bet.
Or make your own by, harvesting, trading for, or otherwise acquiring used or cheap down. Then materials could cost around $20 (if you aren't to picky of shell color).
Otherwise check out underquilts.com or look for a used synthetic uq from arrowhead eq. But these options might be hard to stay within that option.

[LazyCamper]

This has been resolved. I've gotten pads for insulation.