i'll have to check on the gel, i haven't ridden any of the pro-park pads, but i can tell you these are damn comfortable.
to get them, use the contact email that's on the 187 site.
and i highly, highly doubt any homemade custom would last a fraction as long as these. 187 has been making pads for years for the biggest names in skateboarding(ie: Hawk, Mumford, etc..), these are using materials that would cost your average person waaay too much to be beneficial on a cost/labor factor, not to mention the kneecaps are proprietary and damn near indestructable.
