Fort Worth-based TPG Capital and Warburg Pincus LLC are considering a sale or public offering of high-end retailer Neiman Marcus Group Inc., according to several reports. The two investment groups acquired Neiman Marcus in 2005 for $5.1 billion. According to a Bloomberg report, TPG and Warburg are looking for about $8 billion for the retailer. If they don’t find any takers they may seek an IPO, according to the report.