First of all, in fixer formulae, you need to choose acids and bases carefully. If you look at traditional hardnening fixers, you see things like boric acid in addition to glacial acetic acid. Those are the result of seeking thiosulfate compatibility as well as hardner compatibility, besides other things. In non-hardening formulae, selection is easier but still a number of things must be considered besides pH.(posted 8334 days ago)If you just want the benefit claimed for TF-{3,4}, try Ilford Multigrade Fixer (not Universal Fixer) and see if you like the result. As you might get some idea from one of my earlier postings here, in my understanding, you get nearly all the benefit of what's claimed for TF-4 by adjusting the pH to be anywhere between 6 and 7. Ilford Multigrade Fixer is at about 6. (Freshly mixed unused solution may be somewhat lower, but it's still ok.) Sodium metaborate would set the pH higher than this range, and you will smell ammonia.
If you want to try the published formula, but not so willing to go through your thinking process, then stick with sodium metaborate. I do not recommend a quick substitution, even if they are said to work in most general developer formulae.