The command \DeclareMathDelimiter allows to define a delimiter which scales nicely with \left, \big etc. Now the problem I have is that I want to use a particular such delimiter from a different font, in my case the \llbracket and \rrbracket from the stmaryrd package. So the code for doing that would be
However, this requires the math font stmry which will occupy one of the precious 16 math alphabets as soon as one actually uses the command.
Since I don't need any other symbols from that font, I would like to avoid that. I managed to access a single glyph from other fonts as described e.g. in the answers to
but it is not clear to me how one can do that to get the above delimiter feature. Ultimately, I want to use the left & right version in combination with the \DeclarePairedDelimiter command from mathtools.