Ah, that makes sense. A lot easier for me to do than you I expect (part making is fairly complex!) Here is a part that has the breadboard image from the dual part.
18650-battery-holder-alt.fzpz (5.8 KB)
A note of caution (which you already may be aware of!), LIPO batteries can either catch fire or explode if shorted. So if your students are using actual batteries, you may want to make sure you have cells with overload protectors in them. The usual 18650 cells do not have overload protectors although apparently some cells do now!
Peter