My RV has a 50 amp service. Is their a converter available that will allow me to plug into a 30 amp service and still use two air conditioners? Are they reliable? Who makes them and what do they cost?

Let me Google that for you.

You need to know the ratings of the A/C's to know if a 30A-120v supply will be enough.

Think about it. You are going(adapting) from a 120/240v-50A supply, to a 30A-120v supply.
The former is a potential 12,000 watts worth of power. The latter is a potential 3,600 watts worth of power. Do you think there is a difference? ;)