Replace an upright Greek math alphabet in mtpro2

I need to replace the gamma and upright uppercase Gamma alphabets in mtpro2 with their counterparts from newtxmath in both normal and bold styles. I asked a related question, viz., How to replace certain Greek letters in mtpro2 with their counterparts from newtxmath, but got half the answer. For \gamma, the problem is solved, but for \Gamma it isn't. I tried the following workaround:

\DeclareSymbolFont{newtxletters}{OML}{ntxmi}{m}{it}
\SetSymbolFont{newtxletters}{bold}{OML}{ntxmi}{b}{it}
\DeclareMathSymbol{\Gamma}{\mathord}{newtxletters}{0}


but it gave me the italic version of \Gamma. I know that mtpro2 and newtxmath have different (and incompatible) output encodings, but there must be some workaround. To summarize, here is a MWE:

\documentclass[12pt,a4paper]{article}
\usepackage[T1]{fontenc}
\usepackage{tgtermes}
\usepackage{amsmath,amssymb,amsfonts}
\usepackage[lite]{mtpro2}
\usepackage{bm}

\begin{document}

$\gamma \ \bm{\gamma} \ \Gamma \ \bm{\Gamma}$

\end{document}


Which outputs

but the required is

• Note that if you have access to the "full" (rather than the "lite") version of the mtpro2 package, you will have access to the font package's bold-Gamma symbol. In my opinion, the regular-weight and bold-weight versions of the \Gamma glyphs produced by the mtpro2 and newtxmath packages are extremely close. What are you trying to achieve by using the newtxmath-based glyphs instead of the mtpro2-based glyphs? Surely there's no meaningful difference in readability. – Mico May 25 '15 at 8:05