I bought this heater for my resin printers :
https://s.click.aliexpress.com/e/_DeuAIGR

As I am using it in different printers, I did not wanted to stick it in only one. 
In the heater there are some magnet at the bottom, but I found that it does not allow a firm enough hold for the device.

I created that support that you can stick in your printers to keep your heater at the right place (using double sided tape).
You can use version with holes to put magnets ( 6x2mm ) or version without holes.
Magnets are not necessary as the fit is quite tight, but if you want to be extra careful like me, use them :)

I hope this will help someone !