ok,,i had scamp put one on mine when i ordered it.
i see no reason why any compitent welder can't hok you up.
they do have bolt on units and most rv dealers and that may be an option for you too.
if your riding a tank of an old steel bike your talking 40 pounds each. a bike rack maybe anouther 20 ponds or so.lets assume you left your waterbottle on your bike and say 150 pounds total. (actually you can guestimate what you actually will load yourself.)
so you compensate your loading in your trailer to move some weight back on your tongue and your good to go.
uh,,,put weight on your trailer tongue that is,,,well,,, never mind,,you know what i mean.