Help NCP in CA

Can I as the non-custodial parent who is current on support make a claim
against the support if a verbal financial agreement was breeched by the
custodial parent for payment of orthodontic bills?

I do not want to make a claim for the entire amount, only an amount that
comes closer to splitting the cost. I help pay for many things above and
beyond the support demand and I think this is a fair arrangement.

We had agreed to split orthodontic bills of about $2650. To keep in good
standing I had to continually make the payment without any help. Now at the
end we owe over $400 and for the services to be completed the balance must
be paid. So, I paid because the CP refused to. The CP has paid less than
$700 and I have paid the rest. I also pay for all insurance out of my own
pocket since my employer only covers 80% of my policy.

This is in addition to verbal agreements regarding me purchasing two
computers one for our son, the other for her other son that is not mine. We
were to split my sons computer and the CP was to pay for the other one.
Needless to say, 3 years later...no payments. Thats over $1200 as well.