tounge and groove MDF panels for staircases

Does anyone know where I can buy tounge and groove MDF panels for staircases. The sheds have panels suitable for horizontal runs but obviously with the stairs having a pitch of 42 degrees I wouldnt be able to cut the required shape out of the panel.
I do have a router and could make my own but if its already available then it will save me some time!
Anyone have amy links of UK suppliers?
EC .
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.