To me, it is not about what is cheapest. The new NVRAM has a 24 to 124 year retention rating on these things. I am more about preserving a game with NVRAM and removing the possibility of batteries being installed so that the games I work on for others and myself outlive me. I have installed over 250 already.
Trying to save $20 now by not putting NVRAM in now will be eaten up changing that coin cell battery every 2 years, which I think are about $2.50 each.
I am really only familiar with what Lock when Lit, Weebly and Pinitech sell.
You can try what you have and change free play to yes and see if it holds that setting without batteries. If it does, you should be golden.