Substitute for fennel bulb?

[swan_tower]

I’ve been given a nice-sounding recipe for pork tenderloin braised in white wine and elderflower liqueur with thyme, red onion, and fennel bulb. But I’m not a huge fan of that last item — what would the chefs among you recommend as a replacement? With or without altering other ingredients (e.g. a different herb, if something else would harmonize better).

Note that due to allergies and/or dislikes, mushrooms and squash are both out.