SHSH blobs- iphone 4s ios 6.1.3?

My iphone 4s has ios 6.1.3 and i want to downgrade to ios 6.1.2 so i can jailbreak my iphone again(it was jailbroken on ios 6.1 but i accidently upgraded).Is there any way i can get the SHSH blobs for 6.1.2 and downgrade my iphone?

Simply put you can't. Doesn't matter whether you have SHSH blobs you can't at this time downgrade any A5 or A6 device, in your case, iPhone 4S. You'll have to wait until the next jailbreak. I know it's hard to resist that temptation to upgrade, but don't do it!