Giro

They come in different sizes for different recumbent seats and in two thicknesses, standard and comfort. They differ from the stock filter foam in that they are firmer, do not compress over the duration of a ride, do not snag clothing, and ventilate much better. Some find them too easy to move/slide/wiggle on. If clothing snagging is your major problem and you are not looking for better ventilation, Bachetta also sells a cover for the Euromesh that reportedly eliminates that problem.

Cost is about $100. If you go to BentRiderOnline and the forum on Bacchetta's web site, these occasionally come up for sale. You can also search thise sites for how others have liked/disliked this pad and other pads. Attaching them is done by a variety of methods. I sewed Velcro on the Ventisit back with monofilament fishing line in the same locations as on the stock seat and velcro the Ventisit on the Euromesh. Others report using industrial adhesive backed Velcro in a similar manner, gluing the velro on, or alternatively using cable ties (which makes the Ventisit more difficult to remove if you want to wash it or mount seat bags or water bottle holders.

p.s. There is another, no cost, alternative to the stock foam. Remove the stock pad, readjust the seat accordingly, and ride with no pad at all. While most do not find this comfortable due to where their shoulder blades rest on the seat frame etc., evidently some find this perfectly comfortable.

Have you cut the bottom most forward most cable tie on the mesh? This is a very common modification; again searching the Bentrideronline and Bachettta forums has more on this.