It is a motorcycle trailer, not a barge. The tongue is not responsible for much weight.
Get a length of square tubing the same dimensions as the tongue (2"x2"?). Make sure it has a decent wall thickness! .095 or .120 is preferable. If you want your tongue to be the same length, cut the old tongue back about 6 inches. Now place the new tube BELOW the original tongue (you want to tip the trailer BACK, right?) and let it extend forward enough so that when you bolt the new ball hitch coupling to it, the ball will be in the same position, but 2" higher. Get two of the squared U-bolts from Fastenal or Home Depot. The 1/4" bolts are prettier, but for safety, get 3/8" or 1/2" U-bolts.
Drill down and run two Grade-8 bolts (5-1/2") through the new tube and old tongue, vertically, so the holes are in the center. Now bolt the new tube to the old tongue with the two U-bolts and use Ny-Lock nuts on them. Hook up your electrical and take it for a shakedown cruise.
Oh, and 12" tires are better than 8" tires because they rotate slower, which reduces the possibility of wheel bearing failure.