Need to replace meter lights with leds Carver amp

Failing the call to Carver,
You could always measure the voltage.
A diode in series, with a dropping resistor may work? Online calculators will allow you to determine the correct resistor.....1/4watt is probably good enough.

A guy on eBay used to sale led lights for Carver amps. They were easy to install as I recall. I used them in my Carver 15cb amp. The look of meter lights were brighter and whiter looking than the original bulbs.

Or you could go here: https://www.ebay.com/itm/113442826103