ISV Accounts solution for Microsoft CRM?

We have a client who would like to use Microsoft CRM for their full client and accounts solution. They have used Sage Line 50 in the past and too small for any of the MS ERP solutions. Does anybody know of an ISV solution which might fit the bill?

I know CRM has its limits and this in my opinion crosses the line but an ISV solution might be a good alternative compared to going back to Sage line 50 with an integration into CRM

Thanks