Yeah Leba mentioned the way to make those pets. An alternative but more flexible solution is have both Str and Con pet in your inventory (more flexible but more expensive for sure XD), so you can have three settings:
1. Poss con pet and switch to Str (+41str+41con during poss)
2. Poss Str and stay str (+82str during poss)
3. Poss con and stay con (+82con during poss)
It's more flexible compared to bringing a con stats str pet, or str stats con pet, but ofc, it's more costly XD