Can I get a breast lift without implants if I'm happy with the size but want perkier breasts?

You only get implants if you want to be larger. Period.
I don't know who it was...but someone started telling patients that they needed to get an implant to get a nice result wtih a lift. Rubbish! In fact, it is better to avoid implants if having a lift.
By definition, any patient needing a lift has skin that has already failed to hold up the existing weight of their breast. Adding weight to that makes no sense. Sure, you have removed skin, but the skin that remains is the same skin that gave way once already.
But for you, who doesn't even want to look any larger, for sure you don't need implants.

Yes, you can absolutely get a breast lift (mastopexy) without implants if you are happy with the size of your breasts but want them to appear perkier. A breast lift focuses on repositioning and reshaping the existing breast tissue, removing excess skin, and tightening the surrounding tissue to lift the breasts and restore a more youthful contour. It can also reposition the nipples and areolae for a more youthful appearance.
This procedure will not increase breast volume, but it will improve the firmness and shape of your breasts, giving them a lifted and more youthful look. If you are content with your breast size and only want a perkier appearance, a breast lift alone is often the best option.
It's important to consult with an experienced plastic surgeon to discuss your goals and ensure you're a good candidate for the procedure. In some cases, if there is a slight loss of volume in the upper part of the breasts, the surgeon may recommend a fat transfer or a small reduction of tissue, but implants are not necessary if you are happy with the size.
Krishna Vyas, MD, PhD, MHSHarvard, Hopkins, & Mayo Clinic Trained Aesthetic Plastic SurgeonNew York, New York

Implants can be very useful in creating architecture and projection, improving asymmetry, and adding extra volume to small or lax breasts that have been depleted by nursing or changes related to weight loss or aging. If you are already happy with your current breast volume adding weight with implants will only defeat the purpose of trying to make them more lifted or perky with a mastopexy. You would be best served by having a mastopexy (or breast lift). If there is a little too much tissue a very small reduction of tissue along with reshaping of the breast with mastopexy will give a very natural and uplifted result. A small deficiency of volume in the upper pole can be corrected with fat transfer and mastopexy. This has the added benefit of liposuction of stubborn areas of fat in the abdomen, flanks and thighs as donor sites for fat (preferred sources for fat transfer).