I am upgrading my chainring to a 28T - but it looks like I need a special tool to extract the ring. Iv found the tool at Bikeinn for £25 but just wondering if there is a cheaper alternative?
It looks very similar to the Cannondale one.
Park Tool LRT-3 is listed for Specialized, Cannondale and FSA
https://www.parktool.com/product/lockring-tool-lrt-3
A decent sharp edged punch and a mallet works absolutely fine if your careful.
Not all tools are designed well for this. Make sure the tool you buy has a good way of keeping it flat and in full contact. Mine has a giant hole that no tool will fit it and when using it, it's really slippy. Hard to remove the ring, and I'm not sure I can tighten up to the required torque putting back together.
FSA use the Cannondale tool standard
I wouldn't want to be using a punch.