I've been using Tascam DR10CS and DR10L recorders for a few years and they've been great. However, there have been several times where it would have been helpful to be able to transmit wirelessly and monitor the audio.

I've been looking at the Rode Wireless GO II and it seems like a great option for us. Unfortunately, unlike the DR10CS or DR10L the Wireless Go II does not have a locking connector on the 3.5mm jack. Does anyone know if there is a way to secure a 3.5mm cable so that someone doesn't inadvertently knock it loose? We film lots of weddings and grooms tend to be kind of rough with these so if we can find some way to secure this cable then these will work but if not then we probably can't use them.

I someone posted on another forum gluing cable holders around the edge and wrapping the cable around it. Not the most elegant solution. Alternatively you could use gaffers tape for less permanent solution attaching the cable to the unit.

+1.. Gaffers tape.
If the input jack is on non-recessed flat surface,replace the plug with a flush-mount right-angle 3.5mm plug which is less apt to get pulled out (or broken). This Calrad 3.5mm TRS plug is decent despite the low cost (https://www.markertek.com/product/m-3-5ras/right-angle-3-5mm-plug-stereo) and an elastic band can be used in lieu of gooey tape,