i just use a bog standard cheap cat litter tray - i buy mine from poundstretcher for £1.29 each. I fill mine with shavings with a layer of hay on the top - for the most part this stops my long-haired pigs dragging them everywhere.
I did try megazorb for a while, but this is like shavings and the longer haired piggies drag it everywhere when they jump in/out of the tray. I also found this cost more as i was buying an 85litre bag almost every 4wks (i clean out the trays every 3-4 days).
The only thing i found that didnt get dragged everywhere was carefresh - but the cost was stupidly high!
If you have a constant supply that you could change daily, you could try lining the trays with newspaper/hay. I personally found newspaper smelt really quickly and my long haired pigs would sit in the wee as it was soaking through the paper - but ive heard it works for others...