Fortunately, the Signature 2.0 uses many codes in common with Marantz receivers.  So things like Volume, Power, etc should work right out of the box.  Other functions can be programmed with some remotes made by UEI.

Cheapest is the Comcast DVR remote, which you can usually find new on eBay for $6 shipped.  Use setup code 31189.
Atlas and some other cable remotes or the RCA RCRP05B will also work. Use setup code Audio 1189.

Here are the functions listed in the CCF file, along with 5 digit EFCs,  Use the 994 command instructions to assign any function not already in the remote.

0 31289
1 31293
2 31281
3 31285
4 31273
5 31277
6 31265
7 31269
8 31257
9 31261
vol up 29305
vol down 29309
mute 29197
up arrow 28793
down arrow 28797
left arrow 28781
right arrow 28769
Menu 9E? 28785
Menu Off 28789
TrebleMenu 29189
DVD A 62149
ExpressVu 06853
DVD 66245
VCR 1 53957
Tuner 31429
TAPE 25285
CD 37573
AUX 60756
Bass Menu 19508
Music 37284
Display 39188
Balance 39268
Movies 39396
Stereo 39380
Sub 33060
Center 33044
Surround 33028
Mono 33124

I doubt you'll find any cheap remotes which accept Pronto Hex.