I purchased a Samsung Galaxy A01 at Best Buy for $59.99 + tax. It seems to work really well. If you order on line you can only order one (1) at a time. I wanted more than one (1) so I place two (2) orders, one right after the other. I placed the online order about midnight and was able to pick it up, at the store, at 10am. I plan on using these phone exclusivity for my train layout, so I did not activate the carrier.
Also, I just found a reconditioned Samsung Galaxy A01 for $29.99 on Straight Talk web site. https://www.straighttalk.com/all-phones/reconditioned-samsung-galaxy-A01.black
I bought a Motorola Moto G6 Play for $38 shipped from an ebay.com vendor: sellingtech13.
It didn't have a SIM card but I was able to install one from a flip phone to get online to download the LocoFi app. I'm not skilled at smartphone use but I was able to get it to control the LocoFi 3 board without the SIM card. To get familiar with LocoFi I set up a "breadboard" of just the components. Here's a video of it:
https://youtu.be/BqdZ6xAUHG4 It works well. Now I'll install it in a loco.
The "Play" version of the G6 has a long-life battery that is replaceable -- most low-priced used Android phones have non-replaceable batteries.
At the suggestion of the LocoFi team I just tried this Tracfone Alcatel TCL A3 phone from Amazon. It worked fine with my existing WPA secured home Wi-Fi network, and it was only $40.