Leak around freshwater sensor wires - what sealant?

Hi, after a bit of sole searching, the 'van is staying and being used regularly again!

However, it appears to have developed a leak in the freshwater tank. It looks like its around the wires coming out of the sensor. It seems like a lot of hassle to remove the sensor, especially for such a small leak, so hoping to bodge it at least for the short term (heading away at the weekend!) from the outside.

What sealant should I use? everything I have (tec7, silicon, plumbers putty) all say not for polyethylene. Is it specialist only stuff, or would I get something in a diy/ hardware shop? And would it have to be passed for potable water for use on the outside?

Thanks

It seems to be where the wires come out of the sensor, rather than around where the sensor goes into the tank. Anyway, went inside to drain the tank to try and look from the inside - the sensor arm was rolling around the bottom of the water tank. Haven't had a chance to get back out and investigate more, but that's the source of the issue I'd say. Not sure I'll bother replacing it (wasn't that reliable anyway), so not sure what I'll do next...