Do you still have yours and if so what is wrong with it .
I have repaired quite a few JD tanks that were splitting at the joint with an hot air gun and some strips of milk bottles which are HDPE same as the tanks are.
If only the plastic body panels were so easy .
If you have never done any before, then have a practice on some cut up milk bottles or even a 20/25 litre drum ( has to be the milky looking type and not coloured ) .
The trick is clean clean clean then heat till just glassy looking but not till it starts to go soft or worse goes brown ( burning ).
Lots of you tube vids , ignore all the ones that tell you a zip tie will fix anything ,
On the tank some where should be the recycle triangle with HDPE ( high Density Polly Ethylene )
Cut a small patch, hold it with a pair of spring loaded tweezers, heat the tank till it just start to go glassy then introduce the patch from down wind till it goes a glassy which will happen very quick because it is thin.
Work out air bubbles while sort of sweeping the head over the parts then let it cool down, stone cold
Pressureise the tank to about 5 psi and listen for leaks
If all is good then cut a bigger piece, about twice the size to cover over the patch .
Smoothing out & removing air bubbles is the tricky bit
I did use some highly polished spoons for starters but in the end I bought a silicon roller cause everything tends to stick .
If I can do it, any mug can .