I have been happy with https://www.amazon.com/gp/product/B000NPT4TK/ as a desktop power supply for a small 2m/70cm mobile radio.

The MXT275 is advertised as being a 15 watt radio drawing 13.8 volts DC - to get amps, divide the power by the voltage, so it should require something in the neighborhood of 15/13.8 amps, or a little more than 1 amp.

The power consumption of the radio may be more than just its output - but even if you doubled that figure, even a relatively small power supply should be sufficient.

Another aspect to consider is the electrical connection - the power supply I linked above has two screw terminals that connect to two bare wires, while the MXT275 has a cigarette-lighter style 12V plug (which can be easily snipped off). If you prefer not to cut the plug off, you'll want to look for power supplies that provide a 12v socket. This might be a contender: https://www.amazon.com/dp/B0002BA570/ but I've never used it so .. ??

50 amps is serious overkill for this application.

I note that this page for the MXT275 https://www.crutchfield.com/S-A5hLcX0wabu/p_102MXT275/Midland-MicroMobile-MXT275.html says that it uses a 5 amp fuse, so that should tell you the upper limit of the potential power draw for the radio.

https://www.amazon.com/dp/B000NPT4TK/ref=cm_sw_r_sms_apa_cKNSxbZP6Z0G3

Get that and you will be good to go. I have one and have powered both a cb and uhf radio that put out 40watts.

This is what you need.

Universal Compact Bench Power Supply - 30 Amp Regulated Home Lab Benchtop AC-to-DC Converter w/ 13.8 Volt DC 115/230V AC Switchable, Screw Type Terminals, Cooling Fan - Pyle PSV300 https://www.amazon.com/dp/B000NPT4TK/ref=cm_sw_r_apan_glt_i_ZZDTTAM7GZB2FAVVWDSP?_encoding=UTF8&psc=1