so to plug this with 2 different mono sources on the 2 mono females would give the 2 same channels in the resulting stereo file among you ?
I don't know what you mean there.
The item you linked to
is probably wired in such a way as to do what I think you want, but it is unclear from the description and the labeling of the connectors
exactly how it is wired. There may be something printed on or molded into the black female connector housings which indicates 'left' or 'tip' on one of them, and 'right' or 'ring' on the other, but the photo doesn't show that and the description doesn't indicate it either.
The colors (and presumably the printed labels, which can't be read in the photo) on the one pictured below makes the connections a lot more clear by indicating that one female leg (black) has it's sleeve wired to the male leg's sleeve and it's tip to the male leg tip, and the other female leg (red) has it's sleeve wired to male leg sleeve as well, but it's tip connected to the male ring. If you insert that male TRS plug into one of the DR2d's input jacks, this 'Y' would route the white input leg to the left channel and the red input leg to the right channel.
I'm pretty sure that's what you are trying to do. Both the 'Y' pictured below (with mono 3.5 TS female jacks), and the 'Y' hoserama linked to (with mono RCA female jacks) will do that and they clearly indicate how they are wired.