You can get 90V DC motors as surplus, those are pretty common.
Reversing a DC motor is a matter of switching the wires to reverse the DC voltage. You can do this with an H-bridge or a relay.
If you have true DC supply, you'd control speed with PWM. If you've got a low voltage motor you might do this. You're probably going to have an AC supply though so phase control, like with an SCR, is required.
There is one low-tech option- a variac. That can feed a transformer or go directly into a rectifier then the motor if the voltage is already appropriate. It may be an expensive part but it is simple.
I've seen some motor speed controls for sale cheap too- the specified use was for plugging in a router- which might do the job.
I suspect the 4-wire servo didn't have a lot of gearing, did it? See, a DC motor is going to be like 10x faster, and slowing it down will only kill the torque. The servo's benefit was also that it was probably set up so that it wouldn't slow down no matter how much you load it. These other DC motor solutions could lead to something that slows down when it hits a hard spot and surges ahead when it has a lighter load.