an option the HD guys have is a variety of aftermarket kits that place an adapter between the oil filter and engine case that diverts the filtered oil to a cooler and then back again to the engine. Some of these have thermostats, fans, and so on.
Space under our motors (where the oil filter resides) is tight but it might be possible to get something in there.
its got me thinking

05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter