i use www.ultimatesponge.com filters. They work great. I think I would modify the PVC fitting a touch if i had the time, but the collect more media and hold up longer than the Hydro's for me.
I use mostly Hydros and maybe a couple sponges made from Ron. I did purchase a couple of those nice little blue sponges that were for sale at the 2008 CatFish Convention and they're working just fine.
Seeing another today reminded me..... I loose more plecos in tanks with hydros. They like to go into the top an then I guess get wedged in. Saved one yesterday. Lost another one today.
I use sponge filters from Angels Plus in my Angels breeding and fry tanks. They have 2 different one, small pore and regular and sell replacment parts. Angelsplus.com