How can I generate RSS with arbitrary tags and enclosures

Right now, I'm using PyRSS2Gen to generate an RSS document (resyndicating a modification of an rss feed that was parsed with feedparser), but I can't figure out how to add uncommon tags to the item.

items = [PyRSS2Gen.RSSItem(    title = x.title,    link = x.link,    description = x.summary,    guid = x.link,    pubDate = datetime(        x.modified_parsed[0],        x.modified_parsed[1],        x.modified_parsed[2],        x.modified_parsed[3],        x.modified_parsed[4],        x.modified_parsed[5])    )for x in parsed_feed.entries]rss = PyRSS2Gen.RSS2(    title = "Resyndicator",    link = parsed_feed['feed'].get("link"),    description = "etc",    language = parsed_feed['feed'].get("language"),        copyright = parsed_feed['feed'].get("copyright"),    managingEditor = parsed_feed['feed'].get("managingEditor"),    webMaster = parsed_feed['feed'].get("webMaster"),    pubDate = parsed_feed['feed'].get("pubDate"),    lastBuildDate = parsed_feed['feed'].get("lastBuildDate"),    categories = parsed_feed['feed'].get("categories"),    generator = parsed_feed['feed'].get("generator"),    docs = parsed_feed['feed'].get("docs"),    items = items)

The original feed has a <show_id></show_id> tag, as well as an enclosure <enclosure url="http://url.com" length="10" type="" /> and I need to include that in the generated version as well.