Plain or textured muslin are both good choices. (I assume, seeing that you are in Canada, that you are talking about English muslin, which is translucent, ratrher that American muslin, which is what is known as calico in England.)
For an approriate patterned fabric you could try http://www.reproductionfabrics.com/shelf.php?ID=3
> To the best of my knowledge, small patterns were mostly used, including spots and stripes. (Their service is very quick, and the fabrics are very nice quality to work with.)
There is a book from the V and A that has closeup pictures of fabrics in the 19th century. http://www.amazon.co.uk/Nineteenth-Cent ... 193&sr=1-1http://www.amazon.com/Lady-Fashion-Barb ... 0500014191
(This is expensive - look for Inter-Library Loan)http://www.amazon.co.uk/Napoleon-Empire ... 8857206505
This is a fairly recent book of an exhibition, and shows original garments and fasion plates.