Easiest solution if you just want to play silently is to buy two power resistors and a 1590b enclosure.
Wire them in parallel to a jack and you have a super low cost load.
Also be sure to drill holes for ventilation.
I did this for amp testing with 2x 16ohm 100w resistors and it gets a little warm to the touch but that's it.
If you want a dedicated line out on it just add a pot, resistor and jack in like the soldano slave out. You would need to go up to a 1590bb for this though.
Also the bugera attenuator is the soldano designed jet city one rebranded.
You can get the same one from mooer, joyo & harley benton too.