Yes—on a brand-new tripod, this should generally be handled as a warranty/retailer issue rather than something you pay to fix yourself. A leg-lock lever breaking after only a few uses suggests either a defective plastic part or incorrect tension on the lock mechanism.

Best first step: contact the retailer or Manfrotto and ask for a warranty replacement part or exchange. If you bought it online in the EU, you may also have strong consumer protections, including return rights and remedies for faulty goods.

Aftermarket options weren’t identified in the answers. A DIY replacement is possible in principle: a 3D-printed lever could work, but the cam area would likely need to be made larger/stronger to spread the load. That said, on a new product, DIY repair is usually a last resort after warranty support.

As for making the part in metal: it may be possible as a custom fabrication, but there’s no indication of an off-the-shelf metal version. A metal part could also change how forces are transferred to the rest of the lock, so it’s not automatically a better fix.

In short: don’t buy a replacement yet—start with the seller/warranty claim.