http://www.skifurniture.com/vsrchairs.htm

http://www.greenmountainskichair.com/

http://www.snowsource.com/generalstore_skifurniture.htm

That last one sells plans too, but $38 seems a bit steep for simple plans! I just go off pictures or find free/cheap plans and substitue skis for wood. Several plans on sale on eBay.