aside from the sherline I think a rotary from tormach or novakon seem to be the next best thing . A while back I bought a decent rotary from little machineshop which I still need to put to work some day but it appears they don't sell it anymore .

The 100mm belt driven could be made to work on light machining if beefed up . It would require a thicker belt or wider pulleys and belt , plus a stepper with a larger diameter shaft . While playing around with mine I noticed a considerable amount of flex on the 1/4" shaft of the motor . I considered modifying mine but in the end it was easier to cut my losses and save it for when I piece my router back together

Another thing I bought which is really nice and another thing I haven't put to work is a parker rotary stage . They are high precision and very expensive , but they can be found on ebay for a reasonable price if a guy is patient or lucky to find the right one right away . I wouldn't do any excessively heavy work with one but they are very well made