They're US made and Swisher is still in business and still lists log splitters. Might start by asking them. If they can't supply a seal kit I bet they can point you in the right direction. A 22 ton is probably a 4" bore and 1.5" or 1.75" rod, but the cylinders are not all built the same even if they are the same size.
swisherinc.com
Good luck!