you could use one of these as an OAG on the DSLR, and use a webcam as the guide cam....?
http://www.teleskop-express.de/shop/...-fuer-CCD.html
But at 248 euro, you may as well just buy a guidescope and camera...like my excellent Orion mini guidescope.....its awesome....
https://www.bintelshop.com.au/Product.aspx?ID=9196 only $119
Cheers
Chris