Can I purchase a new strap for my nania car seat as the dog chewed it.

Junk yard. Google "junk yard" and your location and you should get some hits. Or I like car-part.com. Once you get them, you should be able to access the bolt that holds them in place by moving the seat all the way forward (assuming that we are talking about front seats). There should be a plastic cover that "pops" off with a little influence. Remove bolt, install new/used part.

Need a model number should be on bottom somewhere

Right,
After several months of struggle to find written instructions how to attach the central harness adjustment strap (The one with metal anchor at the end) to the red clip (buckle) strap as seems to be shown in instructions.
I have found number to temtex uk company that supplies nania products to argos on 01162844910, while emailing them on [email protected] had no result. There's no need to attach the two. Central harness adjuster strap has to be detached and pulled by it's front end as far as it goes.
While red clip strap threads through the gap between backrest and the base.
And red clip strap threads through hole (bracket) at the back of the base.

hi normally on all car seats there is a button or a metal plate at the front of the car seat some times it could be under the fabric you need to press and hold while pulling out the strap to your babies size. hope this helps , good luck x

[email protected] will help

hi, please forward email address for relevany instructions

email [email protected]

i have lost instructions for nania 3in1 ihave got all the straps but cant put i t together can i download instructions please help

you wont find a buckle you need to buy new straps safty reasons

ON THE BACK OF YOUR CAR SEAT ARE TWO LATCHES ONE ON EACH SIDE SIMPLY TAKE ONE STRAP AND TAKE OUT THE STRAP THEN ADJUST IT TO YOUR CHILDS FIT REPEAT WITH THE OTHER. LET ME KNOW IF I WAS ANY HELP...