Govind,
FYI, the Customer Credit Limit is applicable by Company and Customer - it is actually within the PSM as follows:
PaymentAgreement Business Object -> CreditLimitAmount element.
The Customer Business Object has an association to one or many Payment Agreements.
If you open a case to ask about this, i'd suggest you add this information in - the developers may get confused if you ask them about a data source related to the Credit Limit on the "Customer" (as it doesn't exist that way)
I'd guess a custom data source would need to be created for Payment Agreement, then joined back to Customer.
This could then be combined with the Customer Invoice / Sales Order data sources.