Reddit reviews Goodnites Durable Underwear Starter Kit Large/X-Large Girl, 7-Count

From a quick Google search, boys Goodnites have more padding in the front, while girls Goodnites have more at the bottom and in the back. That makes it seem like girls Goodnites are definitely better for a female while sleeping on their backs.

I wonder if something like Goodnites' Tru-Fit's could work for you. They're plain (the girls comes in purple, and purple and pink diagonal stripes), and if you stop being able to find the right inserts a regular incontinence pad or liner might work in it's place (apparently the Tru-fit 'underwear' is slightly plasticized on the inside). Alternatively, go with the boys Goodnites, but put a booster where what you're wearing now gets the most wet.