You want B.Com course books for IGNOU so you already have go books from university but except this B.Com course books is also available on various site and here are name of books with their price:

ECO-01 Business Organization 160 ENGLISH
ECO-02 Accountancy-I 160 ENGLISH
ECO-03 Management Theory 160 ENGLISH
ECO-05 Mercantile Law 160 ENGLISH
ECO-06 Economic Theory 160 ENGLISH
ECO-07 Elements of Statistics 160 ENGLISH
ECO-08 Company Law 160 ENGLISH
ECO-09 Money, Banking & Financing Institutions 160 ENGLISH
ECO-10 Elements of Costing 160 ENGLISH
ECO-11 Elements of Income Tax 160 ENGLISH
ECO-12 Elements of Auditing 160 ENGLISH
ECO-13 Business Environment 160 ENGLISH
ECO-14 Accountancy-II 160 ENGLISH

You can online buy this book from Zigmabooks.com website.