Controlling existing motors with resolvers

At work we have a robot with a dead servo drive. The manufacturer is still around, and says that the original drives aren't available by any means. As far as I can tell, the motors are ordinary 3 phase brushless servos, but with resolvers. I can't find any industrial servo drives or systems that use resolvers. A few manufacturers list drives that can take input from a resolver, but of course they all say "call for quote" before I can get any information on the device.

I'm aware of the Mesa 7I49 resolver interface board, and the 8I20 PWM amplifier (which is out of stock). Are there any other industrial servo amplifiers that work like the 8I20?

This is a professional application: I am not going to screw around designing boards, nor will I consider hobby-grade hardware. I'd like the next person who needs to work on this machine to be able to do so.

By providing detailed technical specifications for your servo amplifier and motor, you’ll significantly improve your chances of receiving an accurate answer.

While you wait for PCW to confirm when the 8i20 might be in stock:
You can use other drives to drive motors and still use the existing resolvers, but no idea what exactly would work for you, probably any "voltage mode" drive, and maybe "torque mode" will also work, but you should wait for someone else to chime in and confirm any of this.
I am sure LinuxCNC will work with any setup, not sure about cheap drives plastering all possible options on the label and later finding out they do only step/dir or only +-10V...although some +-10V should work if they do not explicitly require having a tacho attached.
This would mean using a Mesa 7i97T together with 7i49.
In the meantime some more info might help narrow things down, like motor voltage/current/power, resolver type/make/model (very important as i have resolvers that do not work with 7i49, yes i am unlucky as heck), brakes, tacho maybe, etc.

The existing drives are:
Atlas Copco DMC2 31025P (X axis)
DMC2 31025 (Z axis)
DMC2 31025P (C axis) <- This is the dead one. It's also labeled as having been made by Inmotion Technologies AB

The C axis drive is labeled as 240VAC/7A input, 240VAC/7A output, 400Hz max. At the moment I can't see the labels on the other drives, but I will find out their ratings.

The resolvers are part of the motors, so I don't know anything about them (except Z).
The two motors I can get to are:
Wittenstein TPM004-031R-320P-BP1-0301F000 320V, 5.1A max (X axis)
Elmo PSA 90/6-79-P-PMB-4048 230VAC, 6.6A max continuous. Resolver: 56046-01 6-POL (Z axis)

I cannot get to the C axis motor. It's at the bottom center of the robot which is bolted down to the floor. All I know about that axis is that the motor is physically the largest on the robot, has the same color scheme as the X motor and was possibly made by the same company.

I have scoped the resolver signals: the existing drives run them at 4KHz and the resolvers all work as far as I can tell.

The X and Z drives list the same rating as C: 240VAC, 7 Amp output.

Pico Systems has a small board that converts a resolver to look like a standard quadrature encoder. Unfortunately, it can't provide commutation signals, but does provide an index pulse. This board will not work with variable reluctance resolvers, but is designed for "brushless" resolvers such as those made by Harowe Controls and Singer Kearfott. See:
picosystems.store/product/resolver-converter/
for more info.
There are AC servo drives that can operate without the commutation signals, these are often called "sensorless drives".
Jon