LONDON — Stocks, bonds and commodities? Old hat. Once the preserve of the super-rich, or just the eccentric, all kinds of unusual investments from vintage handbags and shares in fine art to rare Pokemon cards are now the happy hunting ground for stuck-at-home punters. Often armed with lockdown-era savings, such amateur investors are seeking higher returns beyond conventional markets where rocketing prices are prompting warnings of bubbles. They have in turn driven prices on some “alternative” assets up several hundred percent higher in the past year. And just like the no-fee trading apps such as Robinhood that enabled hordes of small-time equity traders to rattle seasoned hedge funds during the recent