Take a look at your tight ends. They often work out really well at fullback if you are looking for a mainly blocking fullback. Plenty of tight ends to be found to recruit. Just take a very close look at their stats while recruiting and look very closely meaning if you are at a point where you are mainly trying to recruit 4* recruits, you may drop down to 3* and even possibly 2* to find that TE that is all about the blocking.
In some Pro plays the fullback drops into the flat for passes and TE for the most part have better stats for doing that anyways so if you can find a really powerful blocking TE you are set at fullback in a PRO.