Heater Element Stretched ?

Whether you decide to replace it or not, I think there's no harm having a spare heater and filter for precautionary purposes.

Someone else may be able to advise on particular brands.

I know that Eheim Jager make 25w heaters and this is one of the best makes. I used to have a Visitherm 25w heater in my betta's tank till it finally broke after several years (I'm now using the 50w Eheim Jager that came with the tank I recently sold)

I would always buy a 'respectable' make for heaters. I won't buy cheap unbranded heaters.

A spare heater is essential. One of mine has just failed in a tank in an unheated room. Fortunately I had covered it with a blanket overnight, which I always do in winter to save a bit of electricity. Also, it was a temperate tank, zebra danios, WCM, Odessa and Checkered barbs which are none the worse for going down to 17 degrees for a while. I did have a spare, now I need a new spare, better than needing new fish. I'm tending to agree that cheap heaters are a risk and am substituting mine for better ones one by one.