I would translate that as:
Well, if you really insist, I do have one more.
Basically, the speaker does have one more, but is reluctant to mention it.
This form of には is mentioned here:
(Often times in the form "…には…が", where you repeat a verb or adjective) It means when you will admit to some behavior or condition but any result of that condition or behavior you do not accept or tolerate.
One of the examples given in the definition is:
I'll write a recommendation letter for you, but don't expect anything
By using the
には in the above, the speaker indicates that they will write the recommendation letter, however at the same time they indicate how they are reluctant to do it perhaps because they don't have confidence in writing it.
I believe that じゃ is 関西弁 for a state-of-being
This form of
じゃ is a form of 老人語. In short, often in anime and manga,
じゃ is a stereotypical way of speaking to indicate the person is elderly. It is the same meaning as
だ in standard dialect.