Fix volume/ power on switch - what is the best way

Hi. The 'volume button and contact switch' has come apart. This is the small square brown contact item with 2 round silver contacts.

As this is in 4 separate parts, I assume it isn't repairable. The 'power button' is OK. I think the home button mounting bracket is also OK.

There appears to be a replacement contact part for about £2/$4, but I can't solder this replacement part.

What is the next best part to buy? There is a 'Proximity light sensor on/off power button flex cable' which looks OK.

Thank you for your help!