Univalve is right.
It's difficult enough to find pedals with MIDI input, if you also look for MIDI out or Thru, the list will be really short.
The best way to do this is to replicate the initial clock signal by using a small Midi thru device. Kenton thru-5, pedalSync Midi Splitty, Midi Solutions Thru or Quadra Thru, etc.
You can then plug all your devices with MIDI inputs into the MIDI thru box, in your set up you would have:
Master Clock (drum machine 1/virtual looper)>MIDI thru box
MIDI thru box (output 1)>looper
MIDI thru box (output 2)>drum machine 2
Now, this addresses the lack of MIDI out/MIDI thru but we still have to identify a small footprint looper that can be sync'ed via MIDI. I do not know of any... And as I did not have many decent chinese guitar players in my contacts (should network more in 2014), I went for the Rang III and the Side Car.
As much as it works nicely with MIDI, both pedals together take an entire Pedaltrain mini... Does not really qualify as small footprint!
Digitech and Boss both make small loopers with some form of sync.
Digitech JamSync is proprietary, it uses Start/Stop and Clock signal (very MIDIesque, if you ask me) but they apparently put their own spin on it so that it (again apparently) only works with other Digitech pedals. Maybe they'll stop being daft in the future and will adopt a more MIDI friendly approach enabling more pedals to join the sync.
PedalSync (Molten Voltage) have released a device that converts MIDI Clock signal into tap tempo signal. It's called CTRL-Sync. It works well; I use it to sync my PH-3 to the rest of my pedals.
Like the PH-3, The RC-2 has also a tap tempo input, in theory we could use the CTRL-Sync to sync the RC-2.
MIDI thru box (output 1)>CTRL-Sync>RC-2
Sounds simple enough; however the RC-2 is ready to receive tap tempo info via the dedicated input when it is not used for looping, when the RC-2 plays a loop, it expects Start and Stop info from the input. So this could mean that we need to stop sending a signal in the input when the RC-2 is looping stuff. I'm not entirely sure...
Mods have been done on the pedal itself to have Start/Stop on an extra footswitch and tap tempo on another (
http://tonequestdemos.tumblr.com/).
Separating functions in this manner could the solution: Modding the RC-2 to have the tap tempo input solely dedicated to tap tempo, separated from the Start/Stop function (which could be on its own dedicated footswitch as per the mod). The RC-2 would capture the Master Tempo whilst it's engaged and is not playing loops, the tap tempo info would not conflict with the Start/Stop info when it plays loop.
Now if the Master tempo is changed on the drum machine whilst the RC-2 is playing loops, the change will not be taken into account by the RC-2 until it is stopped but you cannot have everything.
Synching devices nearly always means spending money, wether it is to purchase devices that have have purposely been designed with sync in mind or buying multiple converters and spending time modding devices that cannot initially be synched as they currently are.
On another note the Timeline can be synched via MIDI, there were issues with this functionality but Firmware Rev. 1.42 released earlier this year should have normally solved them.