No I haven't, but here are the datasheets for the parts used in the OpenEphys acquisition board[0], I'm sure they could be swapped out for other parts given anyone's particular constraints. To assemble from scratch the acq board, they are saying it will cost about $1k[1].

[0] https://github.com/open-ephys/acquisition-board/tree/master/...

[1] https://open-ephys.atlassian.net/wiki/display/OEW/Building+i...

FYI, the OpenBCI boards are based on the ADS1299 from TI. They are essentially an Arduino wrapper for the ADS1299.