Such information is never likely to exist to the level you're looking for.
Attempts - such as Medron's, or others - serve to expose the inconsistencies, discrepancies & gaps in this sort of information. Which isn't that suprising, given names of MPLs exist purely for fluff reasons, and have no involvement in anything else in the game universe. There's no master list of equipment or manufacturers anywhere in existance - it's likely the authors either a) crib from past work, b) crib from past work and change a model designation, or c) make something up that sounds good.
As you note, the newer Objective books give general, high-level information. This appears to be as far as the game developers are prepared to go, given the vast and incoherent mass of fluff out there. Trying to fill those gaps isn't going to provide any enhancement to anyone's game of Battletech or Alpha Strike.
Interstellar Operations, still to be released, provides an even higher level abstraction of strategic output intended to let players game at that vast strategic level. Because I've done some work on the Inner Sphere at War system, I can tell you that it's entirely possible to work out the cost to raise an entire regiment of individually-specified 'Mech designs, and for you to have the stats to play it at the BattleTech, Alpha Strike, BattleForce, ACS, SBF etc levels. But it's not going to tell you where that Pontiac autocannon came from.
There are many - such as Medron and others - who enjoy taking the scattered datapoints and working out interpolations that suit them. Others, like me, are happy enough to talk about third-party merchants, end-user certificates, and the nature of interstellar trade in a universe with porous borders and multi-state corporations. The developers are happy for us to do that, and that lets them work on product that's going to make some profit & keep CGL happy ;)
Cheers,
W.