I'm afraid I can't suggest one. Most of the free services are limited (to size or bandwidth or both - heavy usage could run you into a block) or not useful with pure audio files as they want to be able to add adverts - you gets what you pays for. However most ordinary web servers will do perfectly well - you may have space provided by your ISP - provided that they handle 'byte range requests'. I can test for this if you want to try.
In the meantime two points: your filename has spaces in it. Spaces are not allowed in a URL and the feed is handling this correctly by substituting the code %20 for each space, so it's not actually a problem, but I think it's better avoided. Also the 'length' attribute within the 'enclosure' tag is '0' - it should be the file size in bytes. I doubt that this is the cause of the problem - I'm not convinced that the Store takes any notice of it - but it may be adviseable to get it correct if you can.
More seriously you don't have an 'itunes:duration' tag, so the Store won't know how long your file is and it won't show to subscribers until the file has been downloaded. Again this isn't a fatal issue but it's better to provide this tag. The format is HH:MM:SS or MM:SS, e.g. 01:32:45.