Most any HW heater can easily be converted to claim heat from your circ water.
The Alt energy folks have kits that replace the overpressure valve with a heat exchanger unit.
RHEEM does the best job on super insulated units , and they have GRP guts so will last (guarenteed) for decades.
Not small, not cheap, but one purchase should do almost forever.
These are used in farms and resturianrs so 190F water is no problem.