Gluing milliput to polyethylene?

Cyanoacrylate (CA or Supreglue) will bond most hobby resins to polystyrene and ABS plastics.  Polyethylene (ie milk jug plastic) is a different beast and handles differentl.  Doesnt take CA due to its flexibility

There used to be a website titled this to that which gave guidance on cements to adhere different materials

Have a look at this link.  I've never tried it, but it might be what you're looking for.

https://www.loctiteproducts.com/en/products/fix/super-glue/loctite_plasticsbondingsystem.html#:~:text=Loctite%C2%AE%20Epoxy%20Plastic%2025%20ml,-Features%20and%20Benefits&text=The%20activator%20primes%20hard%2Dto,most%20chemicals%20and%20freezing%20temperatures.

Gluing anything to polyethylene is a challenge.  Hot glue will hold but it is still weak  A mechanical connection is best.  There are some vendors that specialize in small screws and fasteners.  Pins and tacks will also work.  Head on other side of the poly part, shaft glued into resin part.