I can relate to that though I've grown to realize over time that it pays to use the right tool for the job. I understand a universal do-it-all tool may be handy in some situations, maybe even reasonably effective under specific circumstances but it will always be a compromise.

IMHO you would do well to avoid the Razel. It looks way too gimmicky and I have doubts about the handle surviving any heavy prying. The hacking knife or the EOD tool are two simple alternatives, can be modified easily and would probably work for your purposes.

If you have access to a bench and/or angle grinder, maybe a drill press, you could make exactly what you need yourself.
Any suitable stock of carbon steel at least 1/4"-5mm and properly heat treated should be ok. Do NOT attempt to modify a file - they tend to be very hard and barely tempered at all so a file will surely break if subjected to any lateral pressure. Also, the teeth tend to be so hard they will take a heavy toll on whatever grinding tools you're using in short order. A short bill hook or similar pruning tool would be a better choice, tempered a bit softer and shouldn't be to difficult to modify. If all else fails, a section of a leaf spring is easy to find, it's already tempered just right. Of course, you will need to cool the steel while working so as not to ruin the temper. If you have the means and knowledge to do your own heat treating then so much the better.

Anyway, just my 2 cents from an amateur jack-of-all-trades and part-time bladesmith. Good luck whichever option you pick eventually.