My local Sears here in Washington doesn't carry trailer tires
and won't balance lug-centric tires.
Domenica, the thing about trailer tires is to keep them properly pumped up and avoid driving fast, especially in hot weather on hot roads.
WDH is weight
distributing hitch, which takes some tongue weight
off the rear of the tow vehicle and spreads it to the front axle
and the trailer axle
. WDH alone provides some stability but does not itself provide any sway control, however, some WDHs can have sway control built in. Equalizer provides friction sway control and Reese has a dual cam system.