I don’t know of any, but if your intent is to select which of two left channel speakers is connected to the left channel monoblock, and which of two right channel speakers is connected to the right channel monoblock, and assuming you can find a selector that is suitable in all respects other than having common negative terminals (including the ability to handle the high power levels that may be involved, given the high power capability of your amps), you might consider using two such selectors, one for each channel.
That approach would result in the negative output terminals of the two monoblocks never being connected together, and the fact that the negative terminals of the two speakers on a given channel would always be connected together (and to the negative output terminal of the corresponding monoblock) won’t matter.
If your intent is to choose which of two amplifiers is routed to a single speaker on each channel, however, it would of course be a different story.
Just a thought. Regards,