No.1 Flowers for your wife
No.2 Chocolates for your wife
No.3 Wine for your wife
No.4 Tell your wife "I don't need anything for the bike, it's fine as it is".
But don't get carried away, there's No.5
No.5 Start planning a trip with your spare funds. Any trip soon, and make it easy for yourself you've money in the budget for hotels and new tyres, and credits for a bit of time off.
Happy Birthday, you deserve it!!!