The apocryphal hydraulic ram trick sounds like a neat idea. The tops of the fork leg can be sealed no problem, although I feel that maybe attempting it whilst hiding behind a blast proof screen might be a good idea 
Looking at the bearings closer I see one problem with this and that is they're slotted to allow oil to blow past.
The bushes are interference fit with no retaining clips. Interesting point about whether they truly are aluminium backed or PTFE composite – I'm not sure.The original manufacturer is in Switzerland – DT Swiss – and no longer holds spares but did indicate the bearings are not necessarily specific to this industry
It seems that official manufacturer tools are very few and far between – and in most cases their recommendation is to replace the whole lower assembly where the bearings are already pressed in – seems a waste. Unfortunately due to the obsolescence within the cycling industry, forks of this particular size are no longer manufactured and therefore to throw the fork away means to throw the whole bike away…
My subsequent research has found a handy guide provided by another fork manufacturer.
**LINK**
They use generic tools that can cater for a variety of bearing sizes. Looks like the bearing removal and replacement tool is available from USA, and is reassuringly expensive.