Hi ,there are several high power servos but in a standard servo size. Usually metal geared and you will not need anymore than a 6 Kgrm /cm power.
However you will see several servos marked as 180 degree turning but they only work if they have a 180 degree driver.
So you will also need a servo expander unit to fit between the rx and the servo. These are incredibly small items about the size of 2 servo plugs. There is a UK firm makes them and there are several available from China. Expect to pay plus or minus £10.
But even if the servos are advertised at 180 or perhaps 160 degree movement they still require another unit.
If you are happy with electronics and can take a servo apart then add a 1K ohm resistor to each side of the feedback pot and this will increase the total throw of the servo. You will need a bit of trial and error here.
I do not know if modern computer tx's can expand the servo signal to match 180 degrees. I expect someone else will know.