@Anonymous wrote:I no longer have credit cards. (I'm the one being confusing, my apologies)
Ouch, that's a score killer. Having open revolving history (revolving = CC's, lines of credit, etc.) is very important in FICO scoring. FICO scores are risk scores, meaning that they attempt to predict your risk of default on a credit product. Since revolving is so much easier to screw up than installment, you're given more points for open, clean revolving history.
If you're going for a mortgage right away, it's probably too late to fix this, as you aren't supposed to app for things within six months of the mortgage application. One option would be if you ever had an American Express card, one that actually came from AmEx, as opposed to a BofA AmEx or Citi AmEx or USAA AmEx etc. If you once had an AmEx card of any type, and you didn't "burn" them (had it charged-off, etc.), you can try to get another AmEx and it will show the year that the first one was opened, so it won't look like a new account. But of course, you'd have to be able to qualify for a card.
And this doesn't apply for cards from any other banks. Just American Express.
eta: I should have gone back and re-read screen one. Most of this is covered there. 
I'd say that since your loan originator is advising you to open a secured card, it would be worth following that advice. Otherwise, I don't see any way of getting your score up quickly.
This is one of those cases where the impact on your score varies considerably based on what you already have in your credit mix - another one of those one size doesn't fit all thingies.
Folks with somewhat established credit often see a score hit when opening new accounts, thus the advice to avoid applications 6 months before app'ing for a mortgage.
Folks with no credit cards, and with no bank revolving accounts will see a significant score increase, and it is fine to app before a mortgage. In fact, it's beneficial as the score increase is to your advantage.
In this case, OP's biggest struggle is going to be his time frame. But app'ing for and opening a bank/national credit card is the right thing to do, and the sooner the better IMO. If you knew it would report today - then all would be well. OP's FICO would jump. Typically, we're seeing 20 point jumps for this scenario on these boards, and that is what DH and I both experienced as well.
On a slightly different note, DH and I surprised ourselves by refinancing last year - about a year before we planned to. We had just app'd for several cards (I think DH had four new cards, and I think I had 3). They were all on the reports and all one month old. 
Our scores were fine (we knew that) but I was concerned with our new accounts. Our loan officer went over our reports quite thoroughly - not a single eyebrow as much as twitched. However, we were (are) rebuilders and it was the right thing to do. Established folks have to take a different tack.
OP - what is your time frame? I hate to see you put in a last minute rush. What is your loan officer saying (btw - he/she doesn't seem very FICO savvy as is often the case) about timing?
ETA: And I hope Hauling's suggestion works out perfectly for you - if you have had an Amex, it would be a golden solution.