I run a portfolio for my father in law with a similar set of goals. A diversified set of well selected income securities is how I've chosen to go about it, outside of ETFs as mentioned above. I pick individual issues, and leave them alone.
A couple of choices include TY.P, a pref on a closed end fund. Coverage here is massive, and it trades a 12.5% discount to face value. Current yield is 5.7%. Interest rate risk due to perpetual nature, but if it meets the portfolio goals and you have a long time horizon, it might work.
Other choices include UMH.PR.A and ELS.PR.C, both prefs from mobile home park REITs.
I also have a number of Canadian income securities in this portfolio, things like INN.DB.G and PMT.DB.E, things where I think the coverage is good and the 7% YTM is attractive.
As mentioned above, small positions in higher risk income securities isn't unreasonable, if they're uncorrelated and you like the underlying. I have a small SSRAP position in this portfolio, if you like SHLD. Another position I have in small size is EE.DB in Toronto. 35% yield to maturity, 50% discount to face value. It's a small E&P where the senior lender is looking to reduce exposure, and the debt is nearly due. However, their recent production not yet publicly reported (except through the Alberta gov't system) is decent, and they have reasonable asset/income coverage. I think its highly likely to work out. I own this one myself also (much larger position than in my Father in laws account) as I really like the risk reward here.