As Tetsuwan Convoy has mentioned, there isn't really a 95% character model accurate toy rendition of Ultra Magnus unless you go for a bust or PVC toy.

The closest official one is the Titanium release which isn't exactly a great figure and I would go as far as to say that it's at best 80% character model accurate. However it is somewhat lacking and has crucial design flaws indicative to the Titanium line. It also isn't the best looking sculpt ever although it is the most accurate to the character model.

Also as Tetsuwan mentioned, there are one or two really dodgy looking Masterpiece armor upgrades but they are overly expensive and dodgy.

The balance between the closest and best toy representation of G1 Magnus is the FansProject City Commander upgrade for Classics Ultra Magnus. However it does fall a fair bit short of your 95% character model accuracy mark.

Titanium Ultra Magnus:



City Commander: