If your grill cloth is looking a bit threadbare or is ratty and torn you may wish to consider a new piece. So far, I know of no supplier for an exact replacement of the grill cloth used on Sparton Equasonne radios. However, reproduction grill cloth in various attractive styles is available from several sources on the web. Antique Electronic Supply Sells grill cloth, as does RadioDaze. Grill cloth can also be had from grillcloth.com, who offer 40 different patterns to choose from.
*Unfortunately Grillcloth.com is no longer in business, but some patterns of grill cloth are available from http://richmonddesignsinc.com/.
If your grill cloth is intact but terribly dirty, it can in fact be removed an cleaned. Carefully remove it from the grill by scraping away the original glue around the edges. Your radio may have already started this process for you:-) Grill cloth, new or old, is extremely prone to fraying. It is best to treat the edge with some fray prevention compound (such as FRAY-STOP) which is sold in sewing shops. The cloth can then be carefully washed in cold water using a very mild detergent.