Custom OIDs / DD-WRT Router

I am trying to monitor a router with DD-WRT firmware. The OIDs that I need to use cant be found in any of the MIBs found in OpManager's MIB browser. The maker of this firmware does not provide a MIB database that I can use within OpManager. So my question is, how do I add these OIDs to OpManager so i can use them? See example below

(some of the dd-wrt oids are similar to linux oids, for example for memory info - but they have a .101 at the end whereas linux oids don't therefore I can't use the linux oids).

CPU Usage
1.3.6.1.4.1.2021.10.1.3.1 = 01 min avg, Value is between 0.00 and 1.00.
1.3.6.1.4.1.2021.10.1.3.2 = 05 min avg, Value is between 0.00 and 1.00.
1.3.6.1.4.1.2021.10.1.3.3 = 15 min avg, Value is between 0.00 and 1.00.

For UP and DOWN traffic on the WAN-side:
1.3.6.1.2.1.2.2.1.10.8 = Total Downloaded in Bytes
1.3.6.1.2.1.2.2.1.16.8 = Total Uploaded in Bytes

For memory usage:
1.3.6.1.2.1.25.2.3.1.5.101 = Total available
1.3.6.1.2.1.25.2.3.1.6.101 = Used