Heres my list of prospects the Reds could possible acquire via trade. Only a start as theres many more impressive ones out there, but try to add some of your own keeping within reality.

To start out why not go with a prospect from Krivskys' favorite trading acquantinence, the Minnesota Twins.
Eduardo Morlan
W L ERA G GS SV IP H ER HR BB SO BAA
2 1 2.60 16 0 8 27.2 18 8 0 3 39 .175

High strikeouts and stunning control are a plus but his numbers as a starter last year are just as good if not better and he is only 21.

W L ERA G GS SV IP H ER HR BB SO BAA
5 5 2.29 28 18 2 106 78 27 6 38 125 .202

A second strong candiate pitching wise is Michael Zagurski from Philly. Numbers really show on this 24 year old lefty as he has yet to allow a HR in his minor league carrier. Not only that but he has averaged 16.875 K/9 so far this year.
http://web.minorleaguebaseball.com/m... bp&pid=489448

With the lack of sufficient catching prospects a seemingly quick fix could be as easy as the Rangers Taylor Teagarden who in his first full season this year has maintained a .333 average while knocking out 9HR in only 108AB.
http://web.minorleaguebaseball.com/m...pbp&pid=460003

The Mariners hold a second option as a catcher with Jeff Clement as his progression from AAA is prevented by Kenji Johjima. His increasingly diminishing value due to his stubborness leave him swinging for little more than power alone at the plate. This combined with an unsuprising .244 BA would likely keep Krivsky from wanting him. Regardless his power potential and potentially low asking price are to much to pass up.
http://web.minorleaguebaseball.com/m... p&pid=459943

One of the most reasonable to acquire and probably the easiest would be Neil Walker of the Pirates. Walking away with impressive prospect Brent Lillibridge in the Adam LaRoche deal last year proves the Pirates will deal about anyone away for the right price, which in most cases is little to nothing. Walker is not only a switch-hitter but also posses smooth line drive skills. Converted to third from catcher he is in route to vault up prospect lists soon.
http://web.minorleaguebaseball.com/m... p&pid=435522

Other notable mentions include:
SS Sean Rodriguez LAD
http://web.minorleaguebaseball.com/m...pbp&pid=446481
RHP Dellin Betances NYY
http://web.minorleaguebaseball.com/m...pbp&pid=476454
RHP Kevin Slowey MIN
http://web.minorleaguebaseball.com/m... p&pid=458713
RHP Angelo Morales KC
http://web.minorleaguebaseball.com/m...pbp&pid=460593
1B Joe Mather STL
http://web.minorleaguebaseball.com/m...p &pid=458628

stopping short but the list could go on forever.