This particular lens has a 0.3-metre minimum focusing distance and a 30 mm maximum focal length. The filter size for this lens is 52 mm, so make sure the filters will fit.
From London Camera Exchange
Sigma 30mm F1.4 DC DN Contemporary - For Micro Four Thirds
The product is available from £289.00 at international stores.
This product is also available at 1 unverified merchant.