I suggest that you simply pony-up and purchase the right tool; it won't bust you and will give you plenty time to worry about something else. If you intend to replace the holders you could use a pipe wrench, just do the job when no one is watching and dispose of the evidence in a deep hole. The ironic side of this is this, unless you have the seal holder tool, you will be faced with tightening the new holders with some other tool abortion which may reek havoc with the new holders; far from what the hi-tech geeks call a win-win. ( I played in their sandbox for over 30 years and never got tired of despising them---paid pretty good though...)
I apply the seal holder removal tool before I remove the axle and have never had a problem persuading the holders to loosen, or properly tighten upon reassembly. I've not need to use heat, but it can be your friend.
Like commando I replace the chromed holders with stainless (my business IS stainless), done this on a Triumph and will be doing this on an A65.
I am in a position to lend you my seal holder tool, if you don't have one by now. PM me with contact and I'm happy to discuss the details.
Best wishes.