underquilts.com sells unfilled quilt shells that you can choose to shorten, and wilderness logics sells down in one ounce containers.
Knowledge of how to use gear helps too. Shug's sharing of that info is very helpful.
When I'm unfamiliar with some facet of outdoor gear, I buy used (expecting to resell at a small loss) until I learn more about what I prefer, or what suits my needs.
There is more to using UQs than just the length and thickness specs that we are used to on pads. Leighlo adds grosgrain tabs along the sides of her UQs, so it is easy to pull up the sides with string+bungie cord going over the ridgeline. The extra weight of the cordage is worth the extra warmth derived from the better fit of the UQ.
On my Tewa Freeze UQ (older version of current Antifreeze) I use the cord intended as side tieouts for WBBB, tied over the ridgeline of my non-WB hammock by extending the length of the cord.