Youu can grab the IOS file from another 2600 (if it is the same model/design and same IOS you had before this is better). You can use Ciscos TFTP server or just download one they're pretty simple to set-up (normaly just a plain old install, click next,next...etc).
You don't need to do anything special to get the router to talk to the tftp server. Use the comman below as a guide to copy the IOS from the working Router to your pc running as a TFTP server...in this case I show an older version 11.1 IOS (don't know whay you are using, guessing most likely 12.1? anyhow this will still work the same.
R2#copy flash tftp
System flash directory:
File Length Name/status
1 3928052 igs-i-l.111-24.bin
[3928116 bytes used, 266188 available, 4194304 total]
Address or name of remote host [255.255.255.255]? 10.1.1.1
Source file name? igs-i-l.111-24.bin
Destination file name [igs-i-l.111-24.bin]?
Verifying checksum for 'igs-i-l.111-24.bin' (file # 1)... OK
Copy 'igs-i-l.111-24.bin' from Flash to server
as 'igs-i-l.111-24.bin'? [yes/no] yes
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Now that you have the copy of a good Image for your flash you can hook up the console of the router that had been erased. Make sure the pc that has the TFTP service running on it is connected to a switch or hub with the ethernet interface of the bad router.
Next seeing as the router will load into rommon mode only we need to setup a few values like this:
The variables that you must specify include the following:
IP_ADDRESS—IP address for the router you are using.
IP_SUBNET_MASK—Subnet mask for the router you are using.
DEFAULT_GATEWAY—Default gateway for the router you are using.
TFTP_SERVER—IP address of the server from which you want to download the image file.
TFTP_FILE—Name of the file that you want to download.
You do it like this:
rommon > tftpdnld
rommon 1 > IP_ADDRESS=172.15.19.11
rommon 2 > IP_SUBNET_MASK=255.255.255.0
rommon 3 > DEFAULT_GATEWAY=172.16.19.1
rommon 4 > TFTP_SERVER=172.15.20.10
rommon 5 > TFTP_FILE=/tftproot/c2600-i-mz.bin
rommon 6 > tftpdnld
after the last command the download will begin
note the file path will be different on command line 5 for you as will the name of the image
suggested reading (rommon commands)